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Catalog for 1964-1965 describes the amps with the phrase "(insert quantity) tube performance".
Below I show a hypothetical calculation for each amp then the actual physical number of tubes.
First estimate is that the tube performance count does not include any rectifier, does include the
phase splitter, counts all small tubes as double triodes, and the power tubes as singles whatever.
I am not there yet; anyone out there know anything about this old ad spec, or how it was figured?
Eleven tube performance
Deluxe (not actually called "Eleven tube performance", but "Seven tubes, four dual purpose")
Pro
Tremolux
(2x4)+2=10
7 actual tubes
Twelve tube performance
Bandmaster
Bassman
Concert
(2x4)+2=10
6 actual tubes
Fourteen tube performance
Dual Showman
(2x4)+4=12
8 actual tubes
Fifteen tube performance
Deluxe Reverb
Super Reverb
Vibrolux Reverb
Vibroverb
(2x6)+2=14
9 actual tubes
Eighteen tube performance
Twin Reverb
(2x6)+4=16
10 actual tubes
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02-13-2023 09:18 PM
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I looked in catalogues and John Morrish's Fender Amp Book, but found nothing. None of the descriptions in the catalogue mention the output power of the amplifiers, so perhaps these numbers are a scale of Fender's making. Today, we would expect to be told about Watts, but those were simpler times.
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You may be right, I'm not seeing any power specs (maybe that was difficult or expensive to do back then?)
Originally Posted by Litterick
Source - Fender Catalogs
...edit...
I just looked at the earlier years, the amps have rated power in watts from 1955, not sure why that changed...???
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I recall my first guitar teacher, who was born around 1915 telling me, in the mid 60s, that his amp (a vintage, even then, Gibson) had 10 tubes. Nothing about watts. Just the number of tubes.
So, I'd guess that some people thought about power that way and Fender was trying to impress them.
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Ads are not specs, they’re ads. Listing numbers of tubes in an ad is like listing the number cylinders in a car engine, which is what car makers did in those days. Meaningless without power, torque, and efficiency/performance data, but 8 is better than 6 (in Detroit, anyway).
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IIRC, Fender also didn’t list amplifier weights in their catalogs back then. Even when they came out with the big guns (Showman, 4x6L6 Twin etc), they must not have thought anybody cared about weight. Back then, they were right. Originally Posted by pauln
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If we in addition assume:First estimate is that the tube performance count does not include any rectifier, does include the
phase splitter, counts all small tubes as double triodes, and the power tubes as singles whatever.
- valve rectifier is worth 1 tube performance
- diode rectifier is worth 2 tube performance
Then all the amp specs I've checked (not all of them) seem to add up.
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Rectifier tubes count. Many are dual tubes for full wave rectification. Catalogs don’t always have the right tube lineup, check schematic to see what Fender was claiming.
Danny W.
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Schematics have been checked. Originally Posted by Danny W.
The unit "1 tube performance" is not a known unit of measurement which so far hasn't been found outside of this one single Fender catalog. It's not clear what it is supposed to indicate/measure and its definition hasn't been found yet.
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It’s simply marketing speak for “It’s got X physical tubes that perform X+Y different functions, just as any other amp that uses twin triodes.” It has no real-world significance, just leftover blather from the days when “5-tube superheterodyne radio” told you something about the expected performance.
Don’t overthink it.
Danny W.
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OP started counting triodes/tetrodes (omitting the rectifier) and noticed it almost added up to the numbers in the catalog but not quite.
As far as I can see a (full wave) rectifier tube seems to counts as "one tube performance" while a solid state rectifier seems to count as "two tube performance".
The solid state rectifiers in these Fender amps consist of 6 silicon diodes where 3 diodes are connected in series for each phase to add up their reverse voltage rating. They essentially function like 2 diodes, just like a full wave rectifier tube (today you can replace the 6 diodes with 2 "modern" diodes which have a higher reverse voltage rating).
So it is interesting that Fender decided to count solid state rectifiers as more tube performance.
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Thanks, orri! Originally Posted by orri
I think you're right on the calculation
I guess it meant power and features
For those of us who like number theory 11 12 14 15 18 are contiguous ordered
elements of positive integers which aren't sums of two distinct square integers.
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You know, this reminds me a bit of a couple of things.
End of the 19th century, banjo was a very popular instrument. The number of brackets was seen as an indication of quality, and so some manufacturers put an insane number of brackets on their pots - up to fifty. Two dozen seems to be the upper end of effectiveness. It takes long enough to tension a modern head. Fifty brackets must have been crazy.
In the 1960s, the number of transistors in a radio was seen as an indication of quality - even though you only needed five to make a radio. Manufacturers included numerous useless transistors - not actually connected to anything - so they could advertise “ten transistor radio” or whatever.
The sixties Fender catalogs should probably be seen in this light - not that they ever put useless tubes in the amps, but it was the way electronics were marketed then. Just as, not long after, all sorts of calculations were used for power output - “music power,” and all the others. They could make five watts RMS sound like fifty in the catalog.
Regarding tube rectifiers, as mentioned above, there are single-diode (half wave) and dual-diode (full wave) rectifiers, so to be consistent any full-wave rectifier should be counted as two tubes in the performance calculation.
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All of the amps catalogue have the same number (1) of full wave rectifiers, and same number (1) of half-wave rectifiers. Originally Posted by stevo58
They all have one full wave rectifier for the plate supply voltage. This rectifier is either a tube (a full wave rectifier tube) or solid state (6 silicon diodes, functioning as 2 diodes).
In addition they also have a half wave rectifier for the negative bias supply voltage.
Cathode biased amps (like several tweed Fender amps) don't need a separate rectifier for the bias voltage. But I don't see that any of the amps in this catalogue is cathode biased.
(There is a chance I might have checked the wrong specs for some these amps, I did check quickly, but I didn't double check, each amp series change over time so there is chance of mistakingly checking the the same amp series from a different period).
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A full wave rectifier is a bottle containing two half-wave rectifiers Originally Posted by orri
. It has two cathodes and two anodes. A 35W4 is an example, off the top of my head. Two diodes in one bottle, just as there are two triodes in a 12ax7
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The rectifier tubes used by fender were mostly 5Y3 and GZ34. They are indeed a twin diode tubes with both cathodes connected together on the same pin.
Fender however seems to count these tubes as "one tube performance".
I have never seen a half wave rectifier tube in any Fender amp or any other guitar amp schematic (I've seen them in tube manuals and do know they exist and how they work).
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The 1955 catalog had mostly the correct math, with each dual triode counting as 2, power tubes and rectifiers as one. The only one I see that doesn't add up is the Bassman. If the '64/'65 catalog is counting the SS diode strings it's odd that the accompanying blurb doesn't mention them.
Note that the '55 catalog does have power ratings for all the amps.
Danny W.
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